Glenoidal component, set of such components and shoulder prosthesis incorporating such a glenoidal component

ABSTRACT

A surgeon can select the component in which the axes of symmetry of the components are oriented differently with respect to their rear faces.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet as filed with the presentapplication are hereby incorporated by reference under 37 C.F.R. § 1.57.

FIELD OF THE INVENTION

The present invention relates to a glenoidal component of a shoulderprosthesis and to a set of such components that may be used forconstituting a prosthesis. The invention also relates to a shoulderprosthesis comprising such a 5 component as well as to a method forinstalling such a component.

BACKGROUND OF THE INVENTION

In the domain of shoulder protheses, it is known, for example from U.S.Pat. No. 3,978,528, to constitute a so-called “inverted” prosthesis inwhich a convex articular surface fast with the glenoid cavity and aconcave articular surface fast with the humerus, cooperate in order torecreate a joint at the level of the shoulder. In this type ofprosthesis, the glenoidal component may be formed, as disclosed inFR-A-2 835 425, by a base intended to be immobilized on the glenoidcavity and by an element intended to be mounted on this base anddefining the convex surface of articulation.

Furthermore, it is known from FR-A-2 836 039, to provide a possibilityof mounting an element forming a convex surface of articulation on acorresponding base in different positions, this allowing an adjustmentof the articular surface in height with respect to the glenoid cavity.

The base of the known glenoidal components is provided with a so-called“rear face” intended to abut against a resectioned surface of theglenoid cavity which is normally substantially vertical when the patientis in standing position. Now, it may happen that the upper part of thescapula be worn out or destroyed, to the point of modifying thekinematics of the implant by the displacement of the original centre ofrotation, this having for consequence to limit the movements of thepatient's arm.

It is a particular object of the present invention to overcome thesedrawbacks by proposing a glenoidal component which ensures a correctpositioning of the convex surface of articulation, including when theglenoid cavity is damaged or worn out in its upper part and even in itslower part.

SUMMARY OF THE INVENTION

In that spirit, the invention relates to a glenoidal component of ashoulder prosthesis which forms a convex surface of articulation centredon an axis of symmetry. This component is characterized in that the axisof symmetry of the convex surface of articulation is non perpendicularto a rear face of the component which is intended to abut against theglenoid cavity.

Thanks to the invention, the convex surface of articulation may beinclined downwardly or “slanted” with respect to the rear face of thecomponent, this making it possible to orient this articular surfacecorrectly, including when the bearing surface created in the glenoidcavity by resection is not parallel to the direction of the patient'sspinal column. The invention therefore makes it possible to “compensate”a defect in parallelism between the resectioned surface of the glenoidcavity and the axis of the patient's spinal column.

According to advantageous but non-obligatory aspects, a glenoidalcomponent may incorporate one or more of the following characteristicstaken in any technically admissible combination:

In assembled configuration of the component and when the rear face is 20vertical, the axis of symmetry of the convex surface of articulation isdirected downwardly, moving away from the rear face.

The component comprises a base adapted to be immobilized on the glenoidcavity of a shoulder and an element provided to be mounted on this baseand defining the convex articular surface, while the base is providedwith a substantially planar front face in which is pierced a housing forreceiving a finger for centring the element forming the convex surfaceof articulation, this housing being centred on an axis substantiallyperpendicular to this front face, this front face not being parallel tothe rear face of the base. In that case, the front and rear faces of thebase may together form an angle included between 2° and 18°. The basemay be provided with an axisymmetric surface centred on an axisperpendicular to its front face, this surface being adapted to cooperatewith an internal surface of the afore-mentioned element for centring andimmobilization thereof on the base.

The component may be provided with an anchoring stem which extends in adirection which is not perpendicular to at least a part of its rearface.

The component comprises a base adapted to be immobilized on the

glenoid cavity of a shoulder and an element provided to be mounted onthis base and defining the convex articular surface, while the elementwhich forms the convex surface of articulation is provided with a skirtwhich is non-symmetrical with respect to the axis of the afore-mentionedsurface, which extends this surface and in which is defined, at least inpart, a housing for receiving at least a part of the base. This skirtmay be substantially in the form of a portion of torus. The elementwhich defines the convex surface of articulation is advantageouslyprovided with a bore for passage of a member for manoeuvring a means forconnecting this element on the base, this passage extendingsubstantially in a direction globally perpendicular to this surface butnot merged with its axis of symmetry.

The Invention also relates to a set of glenoidal components for ashoulder prosthesis of the type defined hereinabove which allows asurgeon to select a component of appropriate geometry as a function ofthe effective configuration of the glenoid cavity once the latter isresectioned. This set of components is characterized in that theorientation of the axis of symmetry of the convex surface ofarticulation, with respect to a rear face of each component intended toabut against the glenoid cavity, is variable from one component toanother.

According to a first variant embodiment, the front and rear faces of thebases of the components are not necessarily parallel to each other, inwhich case the angle between these front and rear faces is differentfrom one component to another.

According to another variant, the elements of these components whichform a convex articular surface may each be provided with a skirt, asmentioned hereinabove, the dimensions of the skirts being different fromone component to another.

The invention also relates to a total shoulder prosthesis whichcomprises a 10 glenoidal component as described hereinabove or selectedfrom a set of components as described hereinabove.

Finally, the invention relates to a method for installing a glenoidalcomponent of a total shoulder prosthesis, such a component defining aconvex articular surface centred on an axis of symmetry, this methodcomprising steps 15 consisting in:

milling the patient's glenoid cavity in order to create a bearingsurface for the component,

selecting, from a plurality of glenoidal components of which the axes ofsymmetry of the convex articular surfaces are oriented differently withrespect to their bearing face against the resectioned surface of theglenoid cavity, a component which may be applied against this surface insuch a position that the afore-mentioned axis of symmetry is globallyperpendicular to the direction of the patient's spinal column, and

immobilizing the selected glenoidal component on the glenoid cavity in25 the afore-mentioned position.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more readily understood and other advantagesthereof will appear more clearly in the light of the followingdescription of five forms of embodiment of a glenoidal component and oftwo forms of embodiment of a set of glenoidal components in accordancewith its principle, given solely by way of example and made withreference to the accompanying drawings, in which:

FIG. 1 schematically shows a shoulder prosthesis according to the.invention implanted on a patient in a first configuration.

FIG. 2 is a view similar to FIG. 1 for a prosthesis likewise accordingto the invention, implanted in a second configuration.

FIG. 3 is an exploded side view of the glenoidal component used in theprosthesis of FIG. 2.

FIG. 4 is a view in perspective of a base belonging to the component 15shown in FIG. 3.

FIG. 5 schematically shows a set of glenoidal components incorporatingthe one shown in FIGS. 3 and 4.

FIG. 6 is a view similar to FIG. 3 for a component in accordance with asecond form of embodiment of the invention.

FIG. 7 is a view similar to FIG. 3 for a component in accordance with athird form of embodiment of the invention.

FIG. 8 shows a glenoidal component in accordance with a fourth form ofembodiment of the invention of which the base is shown in side view andof which the element defining the convex articular surface is shown incross section.

FIG. 9 is an exploded view in perspective of the component of FIG. 8.

FIG. 10 is a view similar to FIG. 8 for a component in accordance with afifth form of embodiment of the invention; and

FIG. 11 is a view similar to FIG. 9 for the component of FIG. 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, the prosthesis P shown in FIG. 1comprises a humeral component 1 composed of a stem 11 intended to beanchored in the medullary canal of the humerus H, as well as of ametaphyseal part 12 in which is immobilized a cup 13 made ofpolyethylene defining a concave articular surface S₁ substantially inthe form of a portion of sphere.

In accordance with a variant of the invention (not shown), the componentI does not present a cup 13, the surface S1 being formed by themetaphyseal part which is made of metal.

The prosthesis P also comprises a glenoidal component 2 which defines aconvex articular surface S₂ substantially in the form of a hemisphere.

In order to render the drawing clearer, the component 1 is shown insection, while the component 2 is shown in an outside view in FIG. 1.

The surface S₂ is substantially in the form of a hemisphere and X₂-X′₂denotes the axis of symmetry on which this surface is centred.

Furthermore, Z-Z′ denotes a vertical axis passing through the centre ofthe spinal column of a patient who is standing up.

S_(G) denotes the milled surface of the glenoid cavity G against whichthe component 2 abuts when it is mounted on the glenoid cavity.

Normally, the surface S_(G) is substantially parallel to axis Z-Z′, withthe result that an axis X_(G)-X′_(G) normal to the surface S_(G) andpassing through its centre, is substantially perpendicular to axis Z-Z′,i.e. substantially horizontal when the patient is standing up. In theconfiguration of FIG. 1 which corresponds to a nominal configuration ofimplantation, axes X_(G)-X′_(G) and X₂-X′₂ merge and are bothhorizontal.

However, as shown in FIG. 2, it may happen that the surface S_(G) is notreally parallel to the axis Z-Z′, particularly due to wear of theglenoid cavity G or a partial destruction thereof in its upper part, andeven its lower part. In that case, the surface S_(G) forms a non-zeroangle a with respect to a straight line Z₁-Z′₁ parallel to axis Z-Z′ andpassing through the centre M_(G) of the surface S_(G). When the patientis standing up, the axis X_(G)-X′_(G) forms the same angle a withrespect to the horizontal.

According to the invention, the component 2 is configured so that theaxis X₂-X′₂ of the surface S₂ is substantially horizontal when thepatient is standing up, despite the non-optimal orientation of thesurface S_(G).

The component 2 is shown in exploded side view in FIG. 3 and comprises abase or plate 21 intended to be fixed on the glenoid cavity G; as wellas a metallic element 22, sometimes called “head”, which defines thesurface S₂ and which is provided with a centring finger 23 intended topenetrate in a housing 24 made in the base 21 and centred on an axisX₂₄-X′₂₄ perpendicular to the front face 25 of the base 21 which issubstantially planar and oriented opposite the glenoid cavity when thebase is mounted on the glenoid cavity.

26 denotes the rear face of the base 21 which bears against the surfaceS_(G) when the base is in mounted configuration.

An anchoring stem 27 extends from the surface 26 in a direction parallelto an axis X₂₇-X′₂₇ perpendicular to the surface 26.

The base 21 is also pierced with four orifices 28 for passage of fourscrews 29 represented solely by their lines of axis in FIG. 4.

The front face 25 is in the form of a disc centred on the axis X₂₄-X′₂₄and bordered by a truncated surface 30, centred on the axis X₂₄-X′₂₄ andconvergent opposite the stem 27.

The surface 30 extends all around the front face 25 but joins the rearface 26 over only a part of the periphery of the base 21.

The face 26 is substantially planar and the faces 25 and 26 are notparallel to each other. β denotes the non-zero angle formed between thefaces 25 and 26.

The inclined character of the front face 25 with respect to the rearface 26 of the base 21 makes it possible to “compensate” completely orpartially the inclined character with respect to the straight lineZ₁-Z′₁ of the surface S_(G), as long as the least thick part of the base21, which is shown to the right of FIG. 3, is disposed in the vicinityof the lower part of the surface S_(G), i.e. the part located towardsthe patient's ribs.

When the base or plate 21 has been anchored on the glenoid cavity G asindicated hereinabove thanks to the stem 27 and to the positioning ofthe four screws 29, the element 22 may be placed in position byintroducing the finger 23 in the housing 24 and causing an internalsurface 31 of the element 22 shown in broken lines only in FIG. 3, tobear against the surface 30. The geometries of the surfaces 30 and 31are adapted to obtain a locking in the manner of a Morse cone.

In this way, the relative orientation of the faces 25 and 26 makes itpossible to orient the axis X₂-X′₂ of the surface S₂ downwardly in FIG.2 with respect to axis X_(G)-X′_(G) in its part which projects beyondthe glenoid cavity, i.e. to return this axis into substantiallyhorizontal configuration, while the surface S_(G) is not parallel toaxis Z-Z′.

Taking into account the relative orientation of the faces 25 and 26, thesurface 30 borders the face 25 only over a fraction of the height ofthat part of the based located between the faces 25 and 26. 32 denotesthe portion of peripheral surface of the base 21 which is not formed bypart 30. This surface is out of true.

As is more particularly visible in FIG. 5, a set of glenoidal componentsaccording to the invention may incorporate a plurality of glenoidalcomponents 2 a, 2 b, 2 c and 2 d of which the bases 21 a, 21 b, 21 c and21 d have front faces 25 a, 25 b, 25 c and 25 d which make differentangles βa, βb, βc and βd with respect to their respective rear faces 26a, 26 b, 26 c and 26 d. It will be noted that the front and rear facesof the base 21 d are substantially parallel, the angle βd between thembeing, in that case, zero.

The element 22 associated with each base 21 a, 21 b, 21 c and 21 d maybe the same or be different from one component to another.

In this way, when a surgeon installs a shoulder prosthesis P, he may, asa function of the relative orientation of the surface S_(G) and of theaxis Z-Z′, select a glenoidal component of which the base comprisesfront and rear faces oriented in such a manner as to allow the main partof the defect of orientation of the surface S_(G) to be compensated.

Of course, the number of glenoidal components of a set such as the oneshown in FIG. 5 is not necessarily four. It may be chosen as a functionof the desired precision. In addition, it is not compulsory that, insuch a set, a plate has surfaces which are parallel to each other, asshown to the right in FIG. 5. However, it is noted that the glenoidalcomponent shown to the right of FIG. 5 may be used when the prosthesis Pis to be implanted in the configuration of FIG. 1.

The installation of a total shoulder prosthesis is facilitated by theuse of such a set of components insofar as the surgeon can select aglenoidal component effectively adapted to the patient's morphology,them immobilize this component in a position such that the axis ofsymmetry of the convex articular surface is substantially perpendicularto the longitudinal axis of the patient's spinal column.

In the second form of embodiment of the invention shown in FIG. 6,elements similar to those of the first embodiment bear identicalreferences increased by 100. The glenoidal component 102 of thisembodiment comprises an element 122 which bears a substantiallyhemispherical convex articular surface, this element being identical tothat of the first embodiment. The base 121 of the component 102 alsocomprises an anchoring stem 127. This anchoring stem is centred on anaxis X₂₇-X′₂₇ perpendicular to the front face 125 of the base 121 whichis planar and bordered by a truncated surface 130. The base 121 isprovided with a housing 124 for receiving a finger 123 belonging to theelement 122, this finger being centred on the axis of symmetry X₂-X′₂ ofthe surface S₂. The central axis X₁₂₄-X′₁₂₄ of the housing 124 mergeswith the central axis X₁₂₇-X′₁₂₇ of the stem 127.

This form of embodiment differs from the preceding one in that the rearface 126 of the base 121 is not perpendicular to the axis X₁₂₇-X′₁₂₇,with the result that a non-zero angle β exists between the faces 125,and 126.

In this embodiment, it may be considered that the rear face 126 isprovided with a “heel” or wedge 134 which serves to compensate thenon-optimal orientation of the surface S_(G).

In the third form of embodiment of the invention shown in FIG. 7,elements similar to those of the first embodiment bear identicalreferences increased by 200. The glenoidal component 202 of thisembodiment comprises a 25 base 221 as well as an element 222 which formsa substantially hemispherical articular surface S2 centred on an axisX₂-X′₂ on which a centring finger 223 is also centred.

The front (225) and rear (226) faces of the base 221 are not parallel toeach other and define a non-zero angle β. This embodiment incorporatescertain elements of the first and second embodiments, namely that thesurfaces 225 and 226 are both inclined, in different directions, withrespect to a longitudinal axis X₂₂₇-X′₂₂₇ of an anchoring stem 227 ofthe base 221 in the glenoid cavity.

In the fourth form of embodiment of the invention shown in FIGS. 8 and9, elements similar to those of the first embodiment bear identicalreferences increased by 300. The glenoidal component 302 of thisembodiment comprises a base 321 similar to that of the component shownto the right in FIG. 5, i.e. of which the front (325) and rear (326)faces are substantially parallel to each other and perpendicular to acentral axis X₃₂₇-X′₃₂₇ of an anchoring stem 327.

An element 322 intended to be mounted on the base 321 defines a surfaceS₂ substantially in the form of a hemisphere and centred on an axisX₂-X′₂ which is not parallel to axis X₃₂₇-X′₃₂₇ when the element 322 isin mounted configuration on the base 321. To that end, the portion 322 aof the element 322 which defines the surface S₂ is extended by a skirt322 b in the form of a portion of torus centred on an axis X_(c)perpendicular to axis X₂-X′₂ and tangential to the convex articularsurface S2 in the vicinity of a zone of intersection between thissurface S2 and a plane 1 t perpendicular to axis X₂-X′₂ and passingthrough the centre C2 of the surface S₂. γ denotes the angular amplitudeof the skirt 322, i.e. the angle between the plane π and the rear face322 c of the element 322 intended to be turned towards the resectionedsurface of the glenoid cavity when the component 302 is in mountedconfiguration.

A housing 332 is made inside the element 322, both in the skirt 322 band 25 in the portion 322 a. This housing is intended to receive thepart of the base 321 defined between the surfaces 325 and 326. Thehousing 332 is bordered by a truncated surface 331 convergent in thedirection of the surface S₂, while a surface 330 of the same geometry isprovided on the element 321 between the faces 325 and 326.

333 denotes the circular opening for entrance in the housing 332.

The surface S₂ is pierced with a passage 334 allowing the introductionof a tool in the direction of arrow F₃ up to the interior of the element322, which makes it possible to manoeuvre a screw (not shown) forimmobilizing the element 322 on the base 321. Such a screw may inparticular control the displacement of a finger such as the finger 23 ofthe first embodiment, which is, in that case, threaded, in order to bemeshed with a tapped part of the base 321, and this in accordance withthe technical teaching of FR-A-2 835 425.

X₃₃₄-X′₃₃₄ denotes the longitudinal axis of the passage 334. This axisis perpendicular to the surface S₂ and offset by angle γ with respect toaxis X₂-X′₂.

In the fifth form of embodiment of the invention shown in FIG. 10,elements similar to those of the first embodiment bear identicalreferences increased by 400. The glenoidal component 402 of thisembodiment is made in accordance with the same principle as that of thefourth embodiment, with a base 421 identical to base 321 and en element422 which defines a surface S₂ centred on an axis X₂-X′₂ inclineddownwardly in FIG. 10. This embodiment differs from the preceding one inthat the angular amplitude γ of the skirt 422 b, which extends theportion 422 a of the element 422 defining the surface S₂, is greaterthan in the embodiment of FIGS. 8 and 9, this making it possible toincrease the effect of cant of the surface S₂ with respect to the rearface 426 if the base 421.

The components shown in FIGS. 8 to 11 may be considered as belonging tothe same set of glenoidal components allowing the surgeon to select thecomponent most adapted as a function of the value of the angle γ and ofthe orientation of the resectioned surface S_(G) of the glenoidal cavitywith respect to the longitudinal axis Z-Z′ of the patient's spinalcolumn.

Of course, the number of components of such a set is limited to two.

The characteristics of the different forms of embodiment shown may becombined together in that a base or plate with non-parallel front andrear faces might be used with an element provided with a skirt extendingthe portion of this element defining an axisymmetric convex articularsurface.

The invention also allows a correct implantation of a glenoidalcomponent when the lower part of the scapula is damaged. In that case,it suffices to turn the component with respect to the configurationshown in FIG. 2.

The invention has been shown with two-part glenoidal components.However, it is equally well applicable to one-piece glenoidalcomponents.

What is claimed is:
 1. A glenoid prosthesis comprising: a convex surfaceof articulation centered on an axis of symmetry; a base portioncomprising a rear face configured to bear against the glenoid (G) whenapplied to the patient and a front face perpendicular to the axis ofsymmetry, the base portion configured to augment a degraded surface ofthe glenoid; and a stem comprising a first end extending from the rearface and a second end opposite the first end; wherein the axis ofsymmetry of the convex surface of articulation extends along alongitudinal axis through the first end and the second end of the stem;wherein the base portion is asymmetrical about the axis of symmetry ofthe convex surface; and wherein the axis of symmetry of the convexsurface of articulation is not perpendicular to the rear face.
 2. Theglenoid prosthesis of claim 1, wherein the convex surface is disposed onan articular component, the articular component being mateable to thebase portion.
 3. The glenoid prosthesis of claim 2, wherein a non-zeroangle is defined between the front face and the rear face.
 4. Theglenoid prosthesis of claim 2, wherein the articular component comprisesa projection extending from a side opposite the convex surface and thebase portion comprises a recess configured to receive the projection,wherein when the projection is received in the recess, the articularcomponent is aligned to the basic portion.
 5. The glenoid component ofclaim 4, wherein the projection comprises a finger.
 6. The glenoidprosthesis of claim 1, wherein at least a portion of the rear face isnot perpendicular to a longitudinal axis extending through the first endand the second end of the stem.
 7. The glenoid prosthesis of claim 1,wherein the front face is perpendicular to a longitudinal axis extendingthrough the first end and the second end of the stem.
 8. The glenoidprosthesis of claim 1, wherein the rear face is substantially planar. 9.The glenoid prosthesis of claim 1, wherein the base portion comprises awedge portion providing a larger rear-to-front distance at one area ofthe periphery of the glenoid component than at another area of theperiphery spaced away from the wedge portion.
 10. A glenoid prosthesiscomprising: a glenoid component comprising: a base portion comprising afront face and a rear face configured to bear against the glenoid (G)when applied to the patient, and a stem extending from the rear face,the stem comprising a first end and a second end; an articular componentbeing mateable to the glenoid component, the articular componentcomprising: a convex surface of articulation centered on an axis ofsymmetry, and a mating side disposed between the convex surface and thestem, wherein the axis of symmetry is perpendicular to the front face ofthe base portion and to a plane containing the mating side of thearticular component, and wherein the axis of symmetry of the convexsurface of articulation is not perpendicular to the rear face, whereinthe base portion comprises a wedge portion configured to provide alarger rear-to-front distance at one area of a periphery of the glenoidcomponent than at another area of the periphery spaced away from thewedge portion, wherein a longitudinal axis extending through the firstend and the second end of the stem is non-perpendicular to at least aportion of the rear face forming the wedge portion; and wherein the axisof symmetry of the convex surface of articulation extends along thelongitudinal axis through the first end and the second end of the stem.11. The glenoid prosthesis of claim 10, wherein the convex surface formsa partial sphere.
 12. The glenoid prosthesis of claim 10, wherein themating side comprises a centering finger and the front face comprises areceptacle configured to receive the centering finger when the articularcomponent is mated to the base portion.
 13. The glenoid prosthesis ofclaim 12, wherein the receptacle extends from an opening on the frontface toward the rear face of the base portion.
 14. A glenoid prosthesiscomprising: an articular component comprising a convex surface ofarticulation centered on an axis of symmetry, the articular componentfurther comprising a projection extending from a side opposite theconvex surface; a base portion comprising a rear face configured to bearagainst the glenoid (G) when applied to the patient, the base portionfurther comprising a recess configured to receive the projection; and astem extending from a center of the rear face, the stem comprising afirst end and a second end, wherein the axis of symmetry extends along alongitudinal axis through the first end and the second end of the stem;wherein the axis of symmetry of the convex surface of articulation isnot perpendicular to the rear face, and wherein the base portion isasymmetrical about the axis of symmetry of the convex surface.
 15. Theglenoid prosthesis of claim 14, wherein the longitudinal axis extendingthrough the first end and the second end of the stem is notperpendicular to at least a portion of the rear face.